The invention relates to a heating, ventilation and air conditioning system for a plurality of mass transit vehicles wherein a single microprocessor climate control device is used to automatically heat, air condition and/or ventilate each mass transit vehicle depending upon the desired interior air temperature set within each respective transit vehicle.
The invention also concerns a method of controlling the respective heating, ventilation and air conditioning units of a plurality of mass transit vehicles.
In mass transit vehicles there is a need for more varied control of the inside temperature of a vehicle. This is especially true for light rail passenger service, such as subways, as well as heavy rail (e.g., AMTRAK train service). Presently available heating, ventilation and air conditioning (HVAC) systems for light rail vehicles employ controls that are initially set manually and then operate automatically to regulate the interior temperature of a vehicle to a preset comfort level or range. Moreover, these known climate control devices only provide a limited number of comfort levels and must be adjusted manually, for example by a human operator turning valves, at each vehicle to vary the desired comfort level within each respective mass transit vehicle. U.S. Pat. No. 2,675,998 to Reynolds discloses such an "automatic" climate control device for railway cars.
A climate control device for the passenger compartment of a motor vehicle is described in U.S. Pat. No. 4,289,195 to Bellot et al. This climate control device includes a microcalculator, connected to electronic probes for measuring the temperature inside and outside the passenger compartment, and means for selecting and correcting various modes of operation at a passenger's demand. U.S. Patent No. 4,328,855 to Iwata et al. also relates to an electric control system for an automobile air conditioner, i.e., a climate control system for a single moving vehicle. Neither Bellot et al., nor Iwata et al. describes or discloses a device which can control the interior climate of a plurality of moving vehicles.
A wide variety of climate control devices are known for a multiple room structure or building. These HVAC systems employ a central processor which monitors the ambient air temperature of each room and controls the operation of each room's heating and cooling device to achieve the desired ambient air temperature programmed for each room. Known environmental control systems of this type include those described in U.S. Pat. Nos. 4,284,126 to Dawson and 4,174,064 to Pratt, Jr.
A programmable thermostat which features a memory unit receptive of unit values of temperature desired at different times on different days and a microcomputer with clock for the control unit is described in U.S. Pat. Nos. 4,267,966 to Neel et al. and 4,300,199 to Yoknis et al. While the temperature control unit and programmable thermostats taught by Neel et al. and Yoknis et al. allow for preprogrammed automatic changing of temperature levels based on entered unit values, these devices are for use in a building or other stationary space. Thus, it is known to control individual room temperatures and humidity within a building or a single moving vehicle. In these systems designed for buildings, the individual HVAC units are hard wired to their respective control unit and thus, these programmed climate systems are not appropriate for a climate control device for a plurality of mass transit vehicles.
Despite the availability of microprocessor controlled buildings, known HVAC systems for mass transit vehicles are battery powered, manually actuated and controlled by employing complicated and hazardous manual operations. Since mass transit vehicles may be driverless (i.e., trains operated via microprocessor controlled programs) and thus, no operator is on board to adjust the desired comfort level of a vehicle's passenger compartment, each HVAC system is individually set to a desired comfort level for the day before being placed in service. However, if the day's temperature differs from the expected temperature for the day (e.g., the forecast was for a sunny day, temperature in the 90's but, an unexpected cold front lowered the outside temperature), the vehicle's HVAC unit cannot be easily adjusted to adapt to current weather conditions and continues to operate the HVAC unit in the mode (e.g., air conditioning) set that morning.
Even if the vehicles are driven by operators, it is still necessary to pull a vehicle out of service to make the appropriate changes to known HVAC control units as adjustments are usually made outside the vehicle, for example, underneath a railway car using a voltmeter or other manual device. Additionally, only coarse temperature adjustments can be made to control the vehicle temperature and only two or three preset temperature levels are available to choose from in known mass transit climate control devices. Further, operators still must be sent out early to a train yard or vehich storage area to manually set and turn on a vehicle's HVAC unit before the vehicle is placed into service so that the vehicle's interior is at a comfortable level for its passengers.
Thus, it can be seen that there is a need for a heating, ventilation an air conditioning system which is flexible and simple, and remotely controls a plurality of mass transit vehicles' individual HVAC units. In addition, such an HVAC system should permit very small increments of temperature change and provide smooth automatic climate control all year round without the need for manual adjustments, other than the selection of a desired comfort level from inside the vehicle.